The first is a bug in
/etc/sysconfig/network-scripts/ifup-ppp:

--- ifup-ppp.dist       Thu Oct 15 17:07:52 1998
+++ ifup-ppp    Sun Jan 31 20:31:04 1999
@@ -6,7 +6,7 @@
 if [ "$1" != daemon ] ; then
   # disconnect stdin, out, err to disassociate from
controlling tty
   # so that no HUPs will get through.
-  $0 daemon $*& </dev/null >/dev/null 2>/dev/null
+  $0 daemon $* </dev/null >/dev/null 2>/dev/null &
   exit 0
 fi
 shift

The redirections don't seem to take effect unless they come
before the &.  I discovered this when writing a CGI script
containing
the command /usr/sbin/usernetctl ppp0 up.  Because ifup-ppp
never
disconnected from stdout, Apache never saw stdout closed and
didn't
properly close the HTTP connection.

Doing

   /usr/sbin/usernetctl ppp0 up &> /dev/null < /dev/null

to forcibly redirect stdin/out/err works around the
problem.  Making the
above change to ifup-ppp fixes the root cause.  (Thanks to
James Griffiths <my@clubi.ie> for helping to track this one
down.)

This probably applies to all architectures, but I don't
have access to any others to test on.